The present invention relates to computer numerically controlled (CNC) machining centers and more particularly to evaluating and compensating for misalignments or error offsets associated with the multi-degrees of freedom of motion of a tool point of a rotary cutting tool mounted to a spindle mechanism which in turn is pivotably mounted to the machining center for rotation about a trunnion axis.
CNC machining centers are widely used in industry to manufacture components or parts from different types of materials. These machining centers typically have a rotary spindle mechanism with a tool holder at one end for holding a rotary cutting tool during a machining operation. The spindle mechanism is pivotably mounted to the machining center at an opposite end for rotation about a trunnion axis. These machining centers are set up to have an orthogonal X, Y, Z coordinate system and the computer controller monitors or keeps track of the coordinate location of the rotary tool point of the cutting tool during a machining operation or a machine alignment maintenance procedure.
Inaccuracies, misalignments or error offsets can cause the rotary tool point to actually be at one coordinate location while the computer controller has a different coordinate location stored in memory. These error offsets may be caused by wear of the machining center components, such as bearings, guide ways and the like, from extensive use of the machining center, wear of the cutting tool from use, differences between machines in multiple machine installations, misalignment of machine components during the original machine assembly, misalignment of machine components during a maintenance procedure or the machining center's geometric alignment is otherwise different from those geometric parameters which are planned and programmed into the controller.
These differences or error offsets can result in machining errors during manufacturing of a component. For very critical components which require very precise, accurate machining with small tolerances, such as those used in gas turbine engines for aircraft propulsion, these machining errors can be costly. These components are typically made from expensive superalloy type materials, and if a machining error is present, the component may have to be scrapped or reworked, if possible. If the component with a machining error is used in the final assembly of an engine, that component may have a significantly shorter useful life than expected.
It is accordingly a primary object of the present invention to provide a novel comprehensive three-dimensional rotary tool point compensation method and apparatus for minimizing or eliminating machining errors during a machining operation.
It is another object of the present invention to provide a comprehensive three-dimensional rotary tool point compensation method and apparatus which can be used by the computer numerical control of the machining center to adjust the tool point coordinate location during a machining operation for more accurate control of the machining operation.
These and other objects of the invention, together with the features and advantages thereof, will become apparent from the following detailed specification when read with the accompanying drawings in which like referenced numerals refer to like elements.